Magnetic resonance imaging (MRI) can be an important tool for clinical diagnosis. In some instances, in order to better characterize and stage a disease, multiple images with different contrasts are usually acquired from a patient using a series of MRI pulse sequences, such as proton-density (PD) weighted, T1-weighted, T2-weighted, and fluid attenuation with inversion recovery (FLAIR) imaging among others.
In recent years, specialized pulse sequences have been further developed to provide more sensitive and quantitative measures of physiological information. However, even though many sophisticated MRI sequences and protocols are available, it is challenging to include all the valuable pulse sequences in clinical scans for two main reasons. First, these MRI pulse sequences are often time-consuming and it is impractical to include all of the desired sequences into a single clinical scan session. Second, many of these pulse sequences are vulnerable to motion effects (common in pediatric populations and patients with Parkinson's disease, for example), making it difficult to acquire high-quality and artifact-free data.
Even though several approaches have been developed to try to improve imaging throughput or to reduce motion-related artifacts, they are still significantly limited in several ways.
Clinical MRI protocols can be accelerated with parallel imaging. See, e.g., Sodickson et al., Simultaneous acquisition of spatial harmonics (SMASH): fast imaging with radiofrequency coil arrays. Magn Reson Med, 1997 October; 38(4):591-603; and Pruessmann et al., SENSE: sensitivity encoding for fast MRI. Magn Reson Med 1999; 42(5):952-962. However, the motion artifact remains a concern in parallel MRI.
There are other motion-insensitive pulse sequences, such as PROPELLER, that are promising for producing high-quality MRI data. See, Pipe J G., Motion correction with PROPELLER MRI: application to head motion and free-breathing cardiac imaging. Magn Reson Med. 1999 November; 42(5): 963-9. However, it is believed that the associated throughput is not superior to that of existing clinical imaging protocols. As a result, it remains difficult to include many of the desired state-of-the-art sequences for clinical scans.